1. Field of the Invention
The present invention relates to a fabrication method of a printed circuit board and to a printed circuit board machining apparatus.
2. Description of Related Art
Japanese Patent Application Laid-open No. 2006-41029 has been known as a method for fabricating a printed circuit board having very fine wires. It discloses a method of forming grooves corresponding to a conductor pattern (wiring pattern) on a surface insulating layer of the printed circuit board, depositing a conductor (precursor of the wiring pattern) to the formed grooves and then removing the excessive conductor from the surface side of the printed circuit board. A through hole for connecting a conductor pattern in an inner layer with the conductor pattern formed on the surface is made by laser in case of this technology prior to forming the grooves corresponding to the conductor pattern. This technology allows the printed circuit board having the smooth surface to be formed.
A trial for fabricating a conductor pattern by using an excimer laser whose sectional shape (called as “beam shape” hereinafter) is shaped into a rectangular shape has being carried out as disclosed in Phil Rumsby et. al., Proc. SPIE Vol. 3184, pp. 176-185, 1997.
A technology of forming a blind hole by means of an excimer laser whose beam is shaped into a rectangular shape by using a surface conductor layer as a mask has been also known as disclosed in Japanese Patent Application Laid-open No. Hei. 7-336055.
However, in case of JP Application Laid-open No. 2006-41029, it requires at least (a) a photo-resist application step, (b) a photo-resist curing step, (c) an exposure step, (d) a developing step, and (e) a soft-etching step as processes for forming the grooves. Still more, because almost all of the conductor pattern except for a part of the through hole is in a state of just being placed flatly on the insulating layer, its peel strength is weak.
Furthermore, Phil Rumsby et. al. have not considered means for connecting the conductor pattern of the inner layer with the conductor pattern formed on the surface.
Accordingly, it is an object of the invention to provide a printed circuit board whose peel strength is strong as well as to provide a fabrication method and a printed circuit board machining apparatus for fabricating a printed circuit board that allow a fabrication time to be shortened and a fabrication cost to be reduced.